Communication device and communication method

Abstract

A communication device has a padding unit which adds data to an asynchronous packet to form an integer multiple of the block length, an encryption unit which encrypts the added asynchronous packet and a synchronous packet, and a transmitting unit which transmits the encrypted padded asynchronous packet and the encrypted synchronous packet.

What is claimed is:  
     
         1 . A communication device comprising: 
 a padding unit which adds data to an asynchronous packet to form an integer multiple of a block length;    an encryption unit which encrypts the asynchronous packet added by the padding unit and a synchronous packet; and    a transmitting unit which transmits the added asynchronous packet and the synchronous packet encrypted by the encryption unit.    
     
     
         2 . A communication device according to  claim 1 , further comprising: 
 a data length information adder which adds data length information on the length of the real data of the asynchronous packet to the encrypted added asynchronous packet.    
     
     
         3 . A communication device according to  claim 1 , further comprising: 
 a key management unit which rewrites the key information used for encryption by the encryption unit, based on key rewrite information, and adds the key rewrite information to the encrypted added asynchronous packet.    
     
     
         4 . A communication device according to  claim 1 , further comprising: 
 a copy control information adder which adds copy control information which limits the number of times the asynchronous packet is copied, to the encrypted added asynchronous packet.    
     
     
         5 . A communication device according to  claim 1 , further comprising: 
 an adder which inserts, between the encrypted added asynchronous packets, selected one of control information including data length information on a length of real data of the asynchronous packet, key rewrite information which rewrites key information used for encryption by the encryption unit and copy control. information for limiting the number of times the asynchronous packet is copied.    
     
     
         6 . A communication device according to  claim 1 , further comprising: 
 a receiving unit which receives the encrypted added asynchronous packet transmitted from the transmitting unit;    a decryption unit which decrypts the encrypted added asynchronous packet received by the receiving unit and outputs the added asynchronous packet; and    an extraction unit which extracts real data, except for the data added by the padding unit, from the added asynchronous packet output from the decryption unit.    
     
     
         7 . A communication device according to  claim 6 , wherein the extraction unit detects data length information on a length of the real data of the asynchronous packet and based on the detected data length information, extracts the real data except for the added data, from the added asynchronous packet output from the decryption unit.  
     
     
         8 . A communication device according to  claim 6 , wherein the decryption unit detects key rewrite information which rewrites key information used for encryption by the encryption unit and, based on the latest key information rewritten by the key rewrite information, decrypts the encrypted added asynchronous. packet received by the receiving unit.  
     
     
         9 . A communication device according to  claim 6 , further comprising: 
 a copy function which detects copy control information for limiting the number of times the asynchronous packet received by the receiving unit is copied and copies at least the asynchronous packet within the limit.    
     
     
         10 . A communication device according to  claim 6 , wherein the receiving unit receives selected one of control information including the data length information on a length of the real data of the asynchronous packet, key rewrite information which rewrites key information used for encryption by the encryption unit and copy control information for limiting the number of times the asynchronous packet is copied.  
     
     
         11 . A communication method comprising: 
 adding data to the asynchronous packet to form an integer multiple of a block length;    encrypting the added asynchronous packet and the synchronous packet; and    transmitting the encrypted added asynchronous packet and the encrypted synchronous packet.    
     
     
         12 . A communication method according to  claim 11 , further comprising: 
 adding data length information on the length of the real data of the asynchronous packet to the encrypted added asynchronous packet.    
     
     
         13 . A communication method according to  claim 11 , further comprising: 
 rewriting the key information used for encryption based on key rewrite information, and adding the key rewrite information to the encrypted added asynchronous packet.    
     
     
         14 . A communication method according to  claim 11 , further comprising: 
 adding copy control information for limiting the number of times the asynchronous packet is copied, to the encrypted added asynchronous packet.    
     
     
         15 . A communication method according to  claim 11 , further comprising: 
 inserting, between the encrypted added asynchronous packets, one of the control information including data length information on a length of real data of the asynchronous packet, key rewrite information which rewrites key information used for encryption, and the copy control information for limiting the number of times the asynchronous packet is copied.    
     
     
         16 . A communication method according to  claim 11 , further comprising: 
 receiving the encrypted added asynchronous packet transmitted;    decrypting the encrypted added asynchronous packet and outputs the added asynchronous packet; and    extracting real data except for the added data from the added asynchronous packet.    
     
     
         17 . A communication method according to  claim 16 , wherein data length information on a length of the real data of the asynchronous packet is detected and, based on the detected data length information, the real data except for the added data is extracted from the decrypted added asynchronous packet.  
     
     
         18 . A communication method according to  claim 16 , further comprising: 
 detecting key rewrite information which rewrites key information used for encryption is detected, and based on the latest key information rewritten by the detected key rewrite information, the encrypted added asynchronous packet received is decrypted.    
     
     
         19 . A communication method according to  claim 16 , further comprising: 
 detecting copy control information for limiting the number of times the asynchronous packet is copied, and copying at least the asynchronous packet within the limit.    
     
     
         20 . A communication method according to  claim 16 , wherein one of the control information including the data length information on a length of the real data of the asynchronous packet, key rewrite information which rewrites key information used for encryption and copy control information for limiting the number of times the asynchronous packet is copied, is received as an exclusive control information packet.